In general, construction machines, such as excavator, usually perform leveling that makes the ground even while moving forward/backward a bucket. The worker should minutely control the boom and the bucket to keep the load, which is applied to the ground by the bucket, uniform in the leveling. Therefore, the worker necessarily feels very tired in the leveling. Further, when the boom is not minutely controlled in the leveling, the force of the bucket applied to the ground is too large such that the bucket cuts into the ground, or the force of the bucket applied to the ground is too small, whereby the leveling is not performed well.
Meanwhile, the bucket is sometimes replaced by an optional device, such as a breaker, in the construction machines. The breaker is an optional device that breaks rocks and is required to always apply predetermined force to the objects to break, such as rocks. However, in the breaker, a reaction that the boom rebounds up occurs when the breaker breaks the objects. Therefore, the worker needs to more minutely control the boom and the breaker.
Recently, a research that makes the bucket apply predetermined force to the objects, such as the ground or rocks, by using the weight of the boom is conducted, in order to remove the problem described above. In particular, since the phenomenon that the boom rebounds up when the breaker operates occurs, it is required to consider the characteristics of the work even if the weight of the boom is used.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.